Posted by Brittni on Sunday, December 5, 2010 at 7:21pm.
an auditorium has 50 rows of seats. THe first row has 20 seats, the row has 21 seats, the third row has 22 seats, and so on. each row having one more seat than the previous row. How many seats are there all together?

Math  MathMate, Sunday, December 5, 2010 at 7:56pm
First row = 20 seats,
second row = 21 seats,
...
nth row = 19+n seats,
...
50th row = 19+50 = 69 seats
Write the number of seats in forward and reverse order:
19 + 69 = 88
20 + 68 = 88
...
44 + 44 = 88
...
69 + 19 = 88

Sum = 50*(88/2) = 2200 seats

Math  Amber, Thursday, May 10, 2012 at 8:19pm
19+n
u#1=19+1
u#1=20
u#50=19+50
u#1=69
50(20+69)/2

Math  sef.Er, Tuesday, January 19, 2016 at 1:35am
ans.. 2225
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